Have setup email on my server with Dovecot and Postfix. My first domain works perfect, everything works fine. Added a second virtual server with a different domain. the Emails work I can send and receive but I get a email back from my first domain saying this email could not be delivered.
I don’t understand your description of the problem.
And, you must include the full error (preferably the full headers in the bounced message), and the related entries in the mail log (don’t send random stuff from the mail log…watch the mail log at the time you try to send a message that fails and give us the entries that show up about that one failed mail). The mail client rarely has any useful information about a server problem, but the headers might contain some clues about where the mail went astray.
Usually a bounce happens when the mail server doesn’t know who is supposed to receive the mail, and has no idea where to forward it. So…maybe something wrong in the virtual map, or maybe you have set mydestination or something else wrong. Sometimes, bounces can happen if you named your server the same as one of the domains you’re managing in Virtualmin.